The Internet blew up yesterday over a picture of what looks like a fuzzy donut. Yes, science has taken it’s first picture of a black hole and yes, it’s a really big deal. In fact, there are a number of good reasons to geek out about this. You can Google around, or you can read below for some of those nerdy details. Here’s what went into the production of this picture, according to the European Southern Observatory (ESO):
Although the telescopes making up the EHT are not physically connected, they are able to synchronize their recorded data with atomic clocks — hydrogen masers — which precisely time their observations. These observations were collected at a wavelength of 1.3 mm during a 2017 global campaign. Each telescope of the EHT produced enormous amounts of data – roughly 350 terabytes per day – which was stored on high-performance helium-filled hard drives. These data were flown to highly specialised supercomputers — known as correlators — at the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory to be combined. They were then painstakingly converted into an image using novel computational tools developed by the collaboration.
To put that in perspective, each of the eight telescopes in the EHT produced the data equivalent of 3,500 full-length movies in 4K every single day. That data was then analyzed and converted back into a viewable image. A Redditor explains how that happened and what that means:
Radio astronomer here! This is huge news! (I know we say that a lot in astronomy, but honestly, we are lucky enough to live in very exciting times for astronomy!) First of all, while the existence of black holes has been accepted for a long time in astronomy, it’s one thing to see effects from them (LIGO seeing them smash into each other, see stars orbit them, etc) and another to actually get a friggin’ image of one. Even if to the untrained eye it looks like a donut- let me explain why!
Now what the image shows is not of the hole itself, as gravity is so strong light can’t escape there, but related to a special area called the event horizon, which is basically the “point of no return” after which you cannot escape. (It should be noted that the black hole is not actively sucking things into it like a vacuum, just like the sun isn’t actively sucking the Earth into it.) As such, what we are really seeing here is not the black hole itself- light can’t escape once within the event horizon- but rather all the matter swirling around and falling in. In the case of the M87 black hole, it’s estimated about 90 Earth masses of material falls onto it every day, so there is plenty to see relative to our own Sag A*.
Now, on a more fundamental level than “it’s cool to have a picture of a black hole,” there are a ton of unresolved questions about fundamental physics that this result can shed a relatively large amount on. First of all, the entire event horizon is an insanely neat result predicted by general relativity (GR) to happen in extreme environments, so to actually see that is a great confirmation of GR. Beyond that, general relativity breaks down when so much mass is concentrated at a point that light cannot escape, in what is called a gravitational singularity, where you treat it as having infinite density when using general relativity. We don’t think it literally is infinite density, but rather that our understanding of physics breaks down. (There are also several secondary things we don’t understand about black hole environments, like the mechanism of how relativistic jets get beamed out of some black holes.) We are literally talking about a regime of physics that Einstein didn’t understand, and that we can’t test in a lab on Earth because it’s so extreme, and there is literally a booming sub-field of theoretical astrophysics trying to figure out these questions. Can you imagine how much our understanding of relativity is going to change now that we actually have direct imaging of an event horizon? It’s priceless!
Third, this is going to reveal my bias as a radio astronomer, but… guys, this measurement and analysis was amazingly hard and I am in awe of the Event Horizon Telescope (EHT) team and their tenacity in getting this done. I know several of the team and remember how dismissed the idea was when first proposed, and have observed at one of the telescopes used for the EHT (for another project), and wanted to shed a little more on just why this is an amazing achievement. Imagine placing an orange on the moon, and deciding you want to resolve it from all the other rocks and craters with your naked eye- that is how detailed this measurement had to be to resolve the event horizon. To get that resolution, you literally have to link radio telescopes across the planet, from Antarctica to Hawaii, by calibrating each one’s data (after it’s shipped to you from the South Pole, of course- Internet’s too slow down there), getting rid of systematics, and then co-adding the data. This is so incredibly difficult I’m frankly amazed they got this image in as short a time as they did! (And frankly, I’m not surprised that one of their two targets proved to be too troublesome to debut today- getting even this one is a Nobel Prize worthy accomplishment.)
You can read more of their comments here. The main thing about this event is that, no matter how scary the future looks, science is still taking steps forward. Every once in a while, science fiction and science fact meld together in celebration of geeky discovery. Be happy, this is a great moment for everyone. 🙂